HBV infection of cell culture: evidence for multivalent and cooperative attachment

Hepadnaviruses do not infect cultured cells, therefore our knowledge of the mechanism of the early stages of virus-cell interaction is rather poor. In this study, we show that dimethylsulfoxide (DMSO)-treated HepG2 hepatoblas toma cells are infected efficiently by serum-derived hepatitis B virus (HBV ) as monitored by viral gene expression and replication markers. To measure virus attachment, a variety of HBV surface proteins (HBsAgs) were conjugat ed to polystyrene beads and their capacity to attach cells was visualized a nd quantified by light microscopy at a single-cell resolution. Remarkably, DMSO increases the attachment efficiency by > 200-fold. We further identify the QLDPAF sequence within preS1 as the receptor-binding viral domain epit ope. Interestingly, a similar sequence is shared by several cellular, bacte rial and viral proteins involved in cell adhesion, attachment and fusion. W e also found that the small HBsAg contains a secondary attachment site that recognizes a distinct receptor on the cell membrane. Furthermore, we provi de evidence in support of multivalent HBV attachment with synergistic inter play. Our data depict a mechanistic view of virus attachment and ingestion.